Backups should always invisible, whether for data files or AC power. The Eaton 5SC UPS stays invisible two ways: the small size makes it easy to hide (or place in kiosks or equipment closets), and the smarts of the machine will test it's own battery regularly so you don't have to worry about such chores. "Not worry about" is high on every list for UPS systems, and Eaton keeps your worries down to a minimum.
This Eaton model, the 5SC-1000, supports 1000 VA/700 Watts, more than enough to power a couple of servers and a couple of desktop shared storage devices for a few minutes. Not much bigger than an industrial 8-slice toaster you'd see in a busy breakfast diner, the all-black case with the small LCD screen in the upper right corner can fit under desks and worktables and on shelves (sturdy shelves, because batteries are heavy).
Other members of the Eaton 5SC family run from 500/350, 750/525, or 1500/1080 VA/Watts. The smallest two have four and six AC outlets, while the largest two (including the one we tested) have eight outlets. With eight plugs, you could put one of these in the center of a four-cubicle module and backup the PC and monitor of all four users (keeping the monitor going in a power loss makes the users far less nervous). These also come in a tower configuration, so however you like your UPS to look and be tucked away, one of the models will fit your needs.
Shipped with the battery disconnected from the electronics, the only work to do for setup is to pull the front faceplate off and plug in a connector that fits in only one direction. Let the system charge for a few hours, and you're in the UPS business.